It doesn't look like nailgun problem:

2015-10-22T04:14:37 info: [628] Run hook ---
priority: 1200
fail_on_error: true
type: shell
uids:
- '1'
parameters:
  retries: 3
  cmd: ruby /etc/puppet/modules/osnailyfacter/modular/astute/upload_cirros.rb
  timeout: 180
  interval: 20

2015-10-22T04:14:46 debug: [628] 280b6a02-9f04-4de8-9fec-94cc22ac7bd4: MC agent 'execute_shell_command', method 'execute', results:
{:sender=>"1",
 :statuscode=>0,
 :statusmsg=>"OK",
 :data=>
  {:stdout=>
    "/usr/bin/glance --os-image-api-version 1 image-create --name 'TestVM' --is-public 'true' --container-format='bare' --disk-format='qcow2' --min-ram='64'  --file '/usr/share/cirros-testvm/cirros-x86_64-disk.img'\nImage 'TestVM' was uploaded from '/usr/share/cirros-testvm/cirros-x86_64-disk.img'\n+------------------+--------------------------------------+\n| Property         | Value                                |\n+------------------+--------------------------------------+\n| checksum         | ee1eca47dc88f4879d8a229cc70a07c6     |\n| container_format | bare                                 |\n| created_at       | 2015-10-22T04:14:43.000000           |\n| deleted          | False                                |\n| deleted_at       | None                                 |\n| disk_format      | qcow2                                |\n| id               | c7866d71-1903-46b0-81cf-29ab189cfb0c |\n| is_public        | True                                 |\n| min_disk         | 0                                    |\n| min_ram          | 64                                   |\n| name             | TestVM                               |\n| owner            | d0c77303dfbf4512986b2d9859716862     |\n| protected        | False                                |\n| size             | 13287936                             |\n| status           | active                               |\n| updated_at       | 2015-10-22T04:14:46.000000           |\n| virtual_size     | None                                 |\n+------------------+--------------------------------------+\n",
   :stderr=>
    "/usr/lib/python2.7/dist-packages/urllib3/util/ssl_.py:90: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.\n  InsecurePlatformWarning\n/usr/lib/python2.7/dist-packages/urllib3/connection.py:251: SecurityWarning: Certificate has no `subjectAltName`, falling back to check for a `commonName` for now. This feature is being removed by major browsers and deprecated by RFC 2818. (See https://github.com/shazow/urllib3/issues/497 for details.)\n  SecurityWarning\n/usr/lib/python2.7/dist-packages/urllib3/util/ssl_.py:90: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.\n  InsecurePlatformWarning\n/usr/lib/python2.7/dist-packages/urllib3/connection.py:251: SecurityWarning: Certificate has no `subjectAltName`, falling back to check for a `commonName` for now. This feature is being removed by major browsers and deprecated by RFC 2818. (See https://github.com/shazow/urllib3/issues/497 for details.)\n  SecurityWarning\n/usr/lib/python2.7/dist-packages/urllib3/util/ssl_.py:90: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.\n  InsecurePlatformWarning\n/usr/lib/python2.7/dist-packages/urllib3/connection.py:251: SecurityWarning: Certificate has no `subjectAltName`, falling back to check for a `commonName` for now. This feature is being removed by major browsers and deprecated by RFC 2818. (See https://github.com/shazow/urllib3/issues/497 for details.)\n  SecurityWarning\n",
   :exit_code=>0}}

As you can see :exit_code=>0 so, it seems that upload_cirros must have let astute know about the failure.